Gas chromatographs comprise an analytical column, a sample introduction channel for guiding the sample to the analytical column, a sample injection unit for injecting the sample into the sample introduction channel, a carrier gas supply unit for supplying carrier gas to the sample injection unit, and a detector (for example, see Patent literature 1). The sample is injected from the sample introduction unit and is conveyed to the analytical column by the carrier gas supplied from the carrier gas supply unit and separated in the analytical column, and the components thereof are detected in the detector provided downstream of the analytical column.
In this sort of gas chromatograph, in order to adjust the carrier gas supply rate from the bottle, a flow controller (flow rate control mechanism) is employed, comprising devices such as a flow rate control valve, pressure sensor, flow rate sensor, etc. mounted on a channel substrate inside which channels are provided.
The channel configuration of a conventional gas chromatograph will be explained using FIG. 5.
One end of carrier gas channel 110, purge gas channel 112 and split gas channel 114 is connected to pipe connection unit 116 provided in flow rate control unit 160. The other end of carrier gas channel 110, purge gas channel 112 and split gas channel 114 is connected to sample introduction unit 102. Carrier gas channel 110 is a pipe for introducing carrier gas into sample introduction unit 102; purge gas channel 112 is a pipe for discharging purge gas for purging the inside of the sample introduction unit 102; and split gas channel 114 is a pipe for discharging sample and carrier gas which are not introduced into analytical column 106. It will be noted that a portion of the carrier gas is used as sparge gas.
Flow rate control unit 160 comprises channels 118, 120 and 122, and one end of these channels 118, 120 and 122 is connected to pipe connection unit 116. The other end of channels 118, 120 and 122 is connected respectively to pipe connection units 126, 140 and 154. A pipe communicating with a bottle for supplying carrier gas is connected to pipe connection unit 126, a pipe for discharging purge gas to the outside is connected to pipe connection unit 140, and a pipe for discharging split gas to the outside is connected to pipe connection unit 154.
In channel 118, from the pipe connection unit 126 side, there is provided a pressure sensor 134, flow rate sensor 135 and flow rate control valve 128. In channel 120, from the pipe connection unit 140 side, there is provided a pressure sensor 148, flow rate control valve 142 and pressure sensor 150. In channel 122, there is provided a flow rate control valve 156.
This flow rate control unit 160, as shown in FIG. 6, can be configured using a channel substrate 161 inside which channels are formed. In the example of FIG. 6, internal channels, i.e. channels 118, 120 and 122 are provided inside the channel substrate 161, holes communicating with each channel are provided on the surface, a connection block is interposed at the locations of those holes, and a pipe connection unit, pressure sensor, flow rate sensor, flow rate control valve, etc. are mounted by means of the connection blocks. The channel connection part of each element is sealed using an O-ring made of fluorine rubber, etc. in order to maintain air-tightness.